MV's Cinema 4D Area light: Editor render shows the direction of the omni light with area shadow. Because the area of the shadow caster is two dimensional, the area being on the xy axis, the light cast shadows that diffuse only on objects perpendicular to the light.
AreaLightTest.c4d

to download this sample file, perform as save as source operation in you browser. Then open the file from Cinema using the open command.